Abstract: Objective: To compare the external apical root resorption of patients with and without periodontitis during the alignment and leveling phase of orthodontic treatment. Methods: 60 adults malocclusion patients were chosen, 30 were periodontal disease,and 30 were not, All did not need extraction and used MBT technique. The magnitude of EARR were detected by using digital paralleling technique. The films were obtained before the orthodontic treatment(T0) ,1(T1)and 6(T2) months after the orthodontic treatment. We compared the magnitude of EARR in different phases between the two groups. Results: EARR occurred in both groups during the alignment and leveling phase, but there was no statistical difference in the magnitude of EARR X(0-2),X(0-1)between the two groups. Conclusion: EARR occurred in both groups, however, the difference was not significant.

Key words: EARR , Periodontitis , Alignment and leveling